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Joseph Priestley

Joseph Priestley

“His versatility, eagerness, activity, and humanity; the immense range of his curiosity, in all things physical, moral, or social; his place in science, in theology, in philosophy, and in politics; his peculiar relation to the [French] Revolution, and the pathetic story of his unmerited sufferings, may make him the hero of the eighteenth century.”—Frederic Harrison, philosopher.

WHAT did Joseph Priestley accomplish that was so noteworthy? His discoveries and writings have influenced the way people view the role of government, the nature of God, and even the air we breathe.

Whether writing about science or religion, Priestley rejected theories and tradition in favor of facts and truth. Let us see how.


After meeting American scientist Benjamin Franklin in 1765, Joseph Priestley—who had only dabbled in science as a hobby—began to conduct experiments with electricity. The following year, his fellow scientists were so impressed by his discoveries that they elected him to the prestigious Royal Society of London.

Next, Priestley turned his attention to chemistry. Within a short time, he discovered several new gases, including ammonia and nitrous oxide (laughing gas). He even infused water with carbon dioxide, thus inventing carbonated water.

In 1774, while experimenting in southern England, Priestley isolated a remarkable gas that made candles burn more brightly. Later, he placed two ounces (60 ml) of that gas in a glass along with a mouse. The mouse  survived twice as long as it would have in a glass filled with regular air! Priestley himself inhaled the gas, and he said that he “felt peculiarly light and easy for some time afterwards.”

Joseph Priestley had discovered oxygen. * Yet, he called the gas dephlogisticated air, assuming that he had discovered ordinary air that lacked phlogiston, a hypothetical substance that was thought to hinder combustion. Priestley’s conclusion was wrong, but many still consider this discovery to be “the very pinnacle of his lifework.”


Just as Priestley believed that preconceived theories hindered scientific truth, so he concluded that tradition and dogma hindered religious truth. Ironically, during his lifelong search for Bible knowledge, Priestley adopted some ideas that were in conflict with what the Bible really teaches. For instance, at one point he did not believe that the Bible was miraculously inspired by God. He also rejected the Bible’s teaching of Jesus’ prehuman existence.

“If science is the pursuit of truth, then Priestley was a true scientist.”—Katherine Cullen, biologist

On the other hand, Priestley exposed false religious teachings that were, and are to this day, widely believed by mainstream religions. He wrote that the truth taught by Jesus and his followers was later corrupted by falsehoods—including the false teaching of the Trinity, the erroneous belief that the soul is immortal, and the worship of images, which is actually condemned in the Bible.

Priestley’s religious ideas and his support of the American and French revolutions incensed his fellow Englishmen. In 1791, a mob destroyed his home and laboratory, and Priestley eventually fled to the United States. Although particularly remembered for his scientific discoveries, Joseph Priestley believed that learning about God and His purpose was of “superior dignity and importance.”

^ par. 10 Earlier, Swedish chemist Carl Scheele isolated oxygen but failed to publish his discovery. Later, French chemist Antoine-Laurent Lavoisier gave oxygen its name.